Ultrasound imaging systems are used in medicine to explore internal areas of a subject's body. Ultrasonic imaging is non-destructive and versatile and can provide high quality diagnostic images.
A typical medical ultrasound imaging system has a transducer, a custom built electronic controller, and a user interface. The transducer typically comprises an array of at least several regularly-spaced piezoelectric transducer elements. The transducer elements may be arranged in any of several different geometries, depending upon the medical application for which the transducer will be used.
The controller drives the transducer to emit ultrasound signals and collects and processes data from the transducer to provide, store, display and manipulate images. The user interfaces for typical ultrasound imaging systems typically include various input/output devices which allow a user to control the operation of the imaging system. The input/output devices typically comprise at least a control panel, a video display, and a printer.
The electronic controller can send and receive electric signals to and from any of the transducer elements. To create a diagnostic image, the controller transmits electrical excitation signals to the transducer elements. The transducer elements convert the excitation signals into ultrasonic vibrations, which are transmitted into the subject's body. The ultrasonic vibrations typically have frequencies in the range of about 2 MHz to about 12 MHz. The ultrasonic vibrations are scattered and reflected by various structures in the subject's body. Some of the reflected and/or scattered ultrasonic vibrations, which may be called echoes, are received at the transducer. The echoes cause the transducer elements to generate electrical signals. After the excitation signals have been transmitted the controller receives and processes the electric signals from the transducer elements.
The resulting image is displayed in real time on a display. The classic presentation of the display, called B-mode, is a two-dimensional image of a selected cross-section of the patient's body. Modern ultrasound systems also provide flow-imaging modes such as Color Doppler and Pulsed Doppler, which show and can help to quantify blood flow.
Recent miniaturization of electronics has enabled the design of a generation of lighter, portable or handheld ultrasound systems. Ultrasound systems described in the patent literature include the following US patents:                U.S. Pat. No. 5,295,485 to Shinomura et al. describes a handheld ultrasound imaging system that can be adapted to support multi element array transducers and includes a beamformer.        U.S. Pat. No. 5,722,412 to Pflugrath et al., U.S. Pat. No. 5,817,024 to Ogle et al., and U.S. Pat. No. 6,203,498 to Bunce et al. describe handheld ultrasound systems built around a set of ASIC (Application Specific Integrated Circuit) chips. The systems include a transducer array, an ASIC transmit/receive front end, an ASIC that includes digitization and digital beamforming capabilities, an ASIC for signal processing and an ASIC for display processing.        U.S. Pat. Nos. 6,251,073 and 6,569,102 to Imran et al. describe a handheld ultrasound system that can construct an image built from multiple transmit/receive acquisitions that are temporarily stored in a memory. The handheld system has the ability to output a diagnostic image built from multiple transmit/receive acquisitions.        U.S. Pat. Nos. 5,590,658, 6,106,472, and 6,638,226 to Chiang et al. describe a handheld ultrasound system that includes a transducer coupled to a CCD-based analog beamformer and post processing electronics. The system uses a separate back-end to further process and display diagnostic images.        U.S. Pat. No. 7,115,093 to Halmann et al. describes a handheld ultrasound imaging system comprising a detachable scanhead coupled to a traditional beamforming module, that is connected via a USB (Universal Serial Bus) port to a commercially available PDA (Portable Digital Assistant). The PDA performs post processing functions to yield ultrasound images.        
The inventors have recognized a need for a handheld ultrasound imaging device that is cost effective and can be configured to operate in multiple different modes to address different application-specific needs.